[repo] Use a connection instead of a session for repo.stats()

[repo] Use a connection instead of a session for repo.gc_stats()

[repo] Use a connection instead of a session for repo.get_versions()

[webconfig] get_repository moved to repoapi

[schemaserial] Replace 'cursor' with 'cnx' We don't have cursors in rql, since execute is synchronous.

[book] basic documentation for LDAPfeed

[testlib] Use session.sessionid instead of deprecated session.id

Add data/pgdb to hgignore patterns PostgresTestDataBaseHandler uses it as datadir.

[test] make unittest_postgres pass Use PostgresApptestConfiguration which starts a postgresql cluster locally for the duration of the test.

[devtools] make PostgresTestDataBaseHandler start its own postgresql Don't depend on postgresql already running on the system, or on a static config. To use this, set the configcls attribute of your CubicWebTC-derived test class to PostgresApptestConfiguration. Caveats: - this won't work with several tests running concurrently from the same directory, since each would start its own cluster with a shared data directory and stomp on each other's toes - you need initdb/pg_ctl in $PATH, e.g /usr/lib/postgresql/$version/bin on Debian/Ubuntu systems. Closes #3489631